Temperature-dependent photoluminescence and Raman spectra from porous GeSi/Si heterostructures

Porous GeSi/Si heterostructures were fabricated by laterally anodization in HF-based solutions. Photoluminescence spectra have been investigated as a function of temperature (77–300 K), showing that porous GeSi has a quite different temperature dependence from that of porous silicon. Raman spectra indicated that the sample structure changed after anodization. Phonon participation and direct recombination of excitons are proposed to be responsible in the light emission processes of porous GeSi and Si, respectively.     

Photoelectric properties of the GeSi/Si heterostructures with self-assembled nanoclusters grown by sublimation molecular beam epitaxy in a GeH4 medium

The photosensitivity (PS) spectra of the GeSi/Si(001) heterostructures with self-assembled nanoclusters grown by sublimation molecular beam epitaxy in a GeH₄ medium have been studied by photo-emf spectroscopy at the semiconductor/electrolyte junction (PSE) and by photo-emf and photocurrent spectroscopy of Schottky barriers including the temperature dependence of the PS spectra in the temperature range of 10–300 K. The bands related to the phonon assisted and phonon-less interband of spatially indirect optical transitions in the GeSi nanoclusters have been observed in the PS spectra even at 300 K. The scatter effect of the GeSi nanoclusters in size and/or in composition on the PS spectrum’s edge shape has been theoretically considered. The emission theory of the photoexcited carriers from the quantum wells of the GeSi/Si nanoclusters built-in to a Schottky barrier (p-tn junction, semiconductor/electrolyte junction) has been developed.     

Low-energy photoluminescence of structures with GeSi/Si(001) self-assembled nanoislands

The photoluminescence spectra of structures with self-assembled GeSi/Si(001) islands are investigated as functions of the growth temperature. It is shown that the shift of the peak of photoluminescence from islands toward lower energies on decreasing the growth temperature is due to the suppression of Si diffusion into islands and an increase in the fraction of Ge in islands. A photoluminescence signal from the GeSi islands is found in the region of energies down to 0.6 eV, which is considerably smaller than the band-gap width in bulk Ge. The position of the peak of photoluminescence from islands is described well by the model of a real-space indirect optical transition with account of the real composition and elastic strains of the islands. Mono-and multilayer structures are obtained with self-assembled GeSi/Si(001) nanoislands exhibiting a photoluminescence signal in the region 1.3–2 μm at room temperature.     

Ge0.05Si0.95/Si异质结单模共面布拉格反射波导光栅的设计与分析

GeSi/Si异质结布拉格反射光栅是硅基光电集成领域一种重要的集成光学器件,分析GeSi/Si异质结的传光特性和布拉格条件,通过求解布拉格光栅方程,得出耦合系数和耦合效率。利用上述原理设计出入射角为66°,波导层的厚度为2μm,光栅长度为4252μm,槽深为0.05μm,光栅周期为0.456μm,滤波带宽为0.214nm,耦合效率为84.1%的1.3μm Ge_0.05Si_0.95/Si异质结单模共面布拉格反射光栅,并用数值模拟了入射光波电场和反射光波电场的分布。     

Controllable Fabrication of GeSi Nanowires in Diameter of About 10 nm Using the Top-Down Approach

Ordered GeSi nanowires with a ~10 nm cross section are fabricated utilizing top-down and Ge condensation techniques. In transmission electron microscopy measurements, the obtained GeSi nanowires exhibit a singlecrystal structure and a smooth Ge/SiO_2 interface. Due to the linear relationship between the cross-section area and the initial pattern size under the self-limited oxidation condition, the cross-section size of GeSi nanowires can be precisely controlled. The Raman spectra reveal a high Ge fraction(up to 97%) and a biaxial strain of the GeSi nanowires. This top-down technique is promising for fabrication of high-performance GeSi nanowire based optoelectronic devices.     

Photoelectric properties and electroluminescence of <Emphasis Type="Italic">p-i-n</Emphasis> diodes based on GeSi/Si heterostructures with self-assembled nanoclusters

This paper reports on the results of investigations into the photoelectric properties and electroluminescence of p-i-n diodes based on GeSi/Si heterostructures with GeSi self-assembled nanoclusters embedded in the i region. The p-i-n diodes are grown through sublimation molecular-beam epitaxy using a vapor-phase source of germanium. The photovoltage spectra of the p-i-n diodes measured at a temperature of 300 K exhibit a photosensitivity band attributed to interband optical transitions in the GeSi nanoclusters. A new approach to analyzing the photosensitivity spectra of the heterostructures containing GeSi thin layers is proposed, and the energy at the edge of the photosensitivity bands assigned to these layers is determined. The electroluminescence observed in the p-i-n diodes at 77 K is associated with the radiative interband optical transitions in GeSi nanoclusters.     

硅基波导与GeSi／Si超晶格探测器之间光电集成器件的研制

用分子束外延法将ＧｅＳｉ／Ｓｉ超晶格结构生长在ｎ＾＋／ｎ Ｓｉ材料上，先后用反应离子刻蚀法形成探测器波志和硅脊波导，经适当工艺实现硅波导与ＰＩＮ探测器之间的光电集成，５Ｖ偏压下ＰＩＮ控制器的最小暗电流为０．８μＡ，最大光响应电流为２．７μＡ，最大总量子效率为１４％，工作波长为λ＝１．３μｍ。     

基于Franz-Keldysh效应的倏逝波锗硅电吸收调制器设计

本文设计了一种基于Franz-Keldysh (FK) 效应的GeSi电吸收调制器. 调制器集成了脊形硅单模波导. 光由脊形硅波导以倏逝波形式耦合进锗硅吸收层. 在硅基锗二极管FK效应实验测试的基础上, 有源区调制层锗硅中的硅组分设计为1.19%, 从而使得器件工作在C (1528–1560 nm) 波段. 模拟结果显示该调制器的3 dB带宽可达64 GHz, 消光比为8.8 dB, 而插损仅为2.7 dB. 关键词： 锗硅 调制器 电光集成     

X-ray spherical wave scattering patterns of the epitaxial Si/GeSi/Si (001) heterosystem

The interference effects of x-ray diffraction topography in the Si/GeSi/Si (001) heterosystem have been investigated. This heterosystem is a film interferometer in which the GeSi solid solution layer of variable thickness serves as a separating gap. A topograph obtained for a 004 reflection (CuK _α radiation) using a spherically bent monochromator demonstrates both maxima of the pendulum solution observed for the case of a thin crystal (1) and interference fringes due to the variable thickness of the separation layer (2). The correlation of effects (1) and (2) with the successive extinction effect of interference maxima on the slope of the diffraction reflection curve is shown by the calculated topographs obtained for the different ranges of the angle of radiation incidence θ (200 and 1400″). The possibility of precisely determining the thickness of the crystal separation layer of an interferometer based on the indicated effect is demonstrated.     

GeSi／Si应变超晶格探测器的制作

介绍ＧｅＳｉ／Ｓｉ应变新材料探测器的制作方法，它不仅与Ｓｉ微电子工艺相兼容，而且还可调节Ｇｅ含量使其禁带宽度满足现代光纤通信器件的要求。     

Specific features of plastic relaxation of a metastable Ge x Si1 − x layer buried between a silicon substrate and a relaxed germanium layer

Heterostructures Ge/Ge _x Si_{1 ? x} /Si(001) grown by molecular beam epitaxy have been investigated using atomic scale high-resolution electron microscopy. A germanium film (with a thickness of 0.5–1.0 μm) grown at a temperature of 500°C is completely relaxed. An intermediate Ge_0.5Si_0.5 layer remains in a strained metastable state, even though its thickness is 2–4 times larger than the critical value for the introduction of 60° misfit dislocations. It is assumed that the Ge/GeSi interface is a barrier for the penetration of dislocations from a relaxed Ge layer into the GeSi layer. This barrier is overcome during annealing of the heterostructures for 30 min at a temperature of 700°C, after which dislocation networks having different degrees of ordering and consisting predominantly of edge misfit dislocations are observed in the Ge/GeSi and GeSi/Si(001) heteroboundaries.     

Efficient evanescent coupling design for GeSi electro-absorption modulator

Efficient coupling from the silicon waveguide to the GeSi layer is the key to success in the GeSi electro-absorption （EA） modulator based on evanescent coupling. A lateral taper in the upper GeSi layer has room for increasing the modulating efficiency and alleviating the sensitivity of the extinction ratio （ER） and insertion loss （IL） to the length of the active region. The light behavior and the effect of the taper are explored in detail using the beam propagation method （BPM）. After optimization, the light can nearly be totally confined in the GeSi layer without any oscillation. The modulator with the designed taper can achieve low IL and high ER.     

Shallow acceptors in Ge/GeSi multi-quantum well heterostructures

The experimental spectra of residual shallow acceptors in strained quantum well Ge/GeSi heterostructures are interpreted on the basis of a new theoretical approach taking into account both confinement and strain effects. It is shown that the main lines in the spectra of undoped samples with narrow quantum wells result from the photoexcitation of the on-edge acceptors that have binding energy two times less than on-center acceptors.     

Role of edge dislocations in plastic relaxation of GeSi/Si(001) heterostructures: Dependence of introduction mechanisms on film thickness

It has been shown that, in the GeSi/Si(001) heterosystem at lattice parameter mismatches of ～2% and more, a small critical thickness of the introduction of dislocations leads to the implementation of the mechanism of induced nucleation of misfit dislocations. This mechanism consists in that the stress field of an already existing 60° dislocation provokes introduction of a secondary 60° dislocation with an opposite-sign screw component. As a result of the interaction of such dislocation pairs, edge misfit dislocations are formed, which do control the plastic relaxation process. This mechanism is most efficient when dislocations are introduced at the GeSi film thickness only slightly exceeding the critical thickness of the introduction of 60° dislocations, and there are threading dislocations. The dominant type of misfit dislocations (60° or edge) in the Ge-on-Si(001) system can be controlled by varying the mismatch parameter in the heteropair.     

The equilibrium composition in GexSi1-x/Si self-assembled alloy quantum dot

<正>The equilibrium composition in strained quantum dot is the result of both elastic relaxation and chemical mixing effects,which have a direct relationship to the optical and electronic properties of the quantum-dot-based device.Using the method of moving asymptotes and finite element tools,an efficient technique has been developed to compute the composition profile by minimising the Gibbs free energy in self-assembled alloy quantum dot.In this paper,the composition of dome-shaped Ge_xSi_(1-x)/Si quantum dot is optimized,and the contribution of the different energy to equilibrium composition is discussed.The effect of composition on the critical size for shape transition of pyramid-shaped GeSi quantum dot is also studied.     

Electro-optical phenomena accompanying electron and hole heating in superlattices and quantum wells GaAs/AlGaAs and Ge/GeSi

New electro-optical phenomena in quantum-well structures, i.e. modulation of the light absorption and birefringence due to carrier heating in a strong electric field, have been investigated. The effects have revealed different features in the three types of structures under investigation, namely: (1) well-dopedn-type GaAs/AlGaAs multiple quantum wells, (2) barrier-dopedn-type GaAs/AlGaAs superlattices and (3) barrier-dopedp-type Ge/GeSi multiple quantum wells. Possible mechanisms of the phenomena have been discussed.     

Raman spectroscopy of strained GeSi alloys deposited on Ge substrates

The Raman scattering method has been successfully used to investigate the properties of GeSi alloys deposited on Ge substrates in this paper. The effect of Si composition and strain in the GeSi alloy on the Raman shifts of Ge-Ge, Ge-Si and Si-Si phonon modes is studied. The relationship between them have been derived by the assumption that the Raman shifts is nearly linear with Si composition and strain in the GeSi alloys. The experimental data show reasonable agreement with the fits.     

Photoluminescence of self-assembled GeSi/Si(001) nanoislands of different shapes

The dependence of the photoluminescence spectra of structures with self-assembled GeSi/Si(001) islands on Ge deposition temperature was studied. The position of the island photoluminescence peak maximum was found to shift nonmonotonically with decreasing Ge deposition temperature. The blue shift of the island photoluminescence peak with the growth temperature decreasing from 600 to 550°C is assigned to the change in the island shape occurring in this temperature interval accompanied by a strong decrease in the average island height.     

Electron Spin Resonance in Heterostructures with Ring Molecules of GeSi Quantum Dots

JETP Letters - Heterostructures with annular groups of GeSi quantum dots grown on Si(001) substrates with GeSi nanodisks embedded beneath the surface are investigated by the electron spin resonance...     

锗硅/硅异质结材料的化学气相淀积生长动力学模型

基于化学气相淀积(CVD)的Grove理论和Fick第一定律,提出并建立了锗硅(SiGe)/硅(Si)异质结材料减压化学气相淀积(RPCVD)生长动力学模型.与以前锗硅/硅异质结材料生长动力学模型仅考虑表面反应控制不同,本模型同时考虑了表面反应和气相传输两种控制机理,并给出了两种控制机理极限情况下的模型.本模型不仅适用于低温锗硅/硅应变异质结材料生长的表征,也适用于表征高温锗硅/硅弛豫异质结材料生长的表征.将模型计算值与实验结果进行了对比,无论是625℃低温下的应变SiGe的生长,还是900℃高温下的弛豫 关键词： SiGe/Si异质结材料 化学气相淀积生长动力学模型 Grove理论 Fick第一定律